5 replies to this topic

[go-fish]

I am designing a closed cooling water system. It comprises of cooling water pump, expansion drum and air coolers. The CW is supplied to multi-stage compressor intercoolers. I would like to know if the flow balancing valve (manual globe or butterfly) for each intercooler can be located on either supply or return or one location has more pros than the other?

I am considering to locate the balancing valve on the supply as I intend to make the isolation valve on the return as locked open to provide an open path to a PSV on the expansion drum for a relief scenario.

[Bobby Strain]

A relief valve on each exchanger is probably less costly than a lock open valve. And you won't have to monitor the valve. It sounds as if this is a small system. Otherwise you would use direct air intercoolers.

 

Bobby

[go-fish]

Process side is hydrogen with up to 93 barg design pressure and cooling water side is 10 barg design pressure. Relief valve for tube leak scenario for liquid displacement case has a large orifice. So instead of providing several large PSVs on each exchanger and an open path is provided to one large on the expansion drum. Of course, this is just a proposal currently being discussed with my organisation’s overpressure protection SME as still need to a check if the back pressure on the exchanger LP side doesn’t exceed 11 barg when the expansion drum PSV is relieving liquid.

Just curious why would a PSV be less expensive than LO valve?

I do not want to digress this topic towards overpressure protection but if we set aside LO valve and point to main query look, is there a preferred location of the manual balancing valve? These should be just set once during commissioning and start-up based on the design flow.

[Bobby Strain]

What you are going to find for a tube rupture case is a tremendous relief rate.  Because all the liquid must accelerate the required pressure will be much greater than 11 bar. It's unlikely that 11 bar is high enough in this instance. If this is a small system, a double pipe exchanger will eliminate the need for overpressure protection resulting from a tube rupture.

 

Bobby

Edited by Bobby Strain, 14 July 2022 - 04:39 PM.

[go-fish]

Already selected double pipe exchanger to eliminate tube rupture. But still need to consider pin hole leak as recommended by the 7th edition of API 521. Due to the high pressure differential between the LP and HP side, liquid displacement case is still significant even for a 3 mm pin hole leak.

Anyone, any feedback on the balancing valve location before this thread becomes an overpressure protection focused and I am being told off for not putting this query in the correct forum? ????

[Bobby Strain]

You need to hire a professional who can conduct a dynamic analysis. The results may show that you need a rupture disk on the heat exchanger. The usual steady state analysis is not sufficient.

 

Bobby